Re: [amsat-bb] MicroOven Beacon-WARNING!

["Mark L. Hammond" <hammond@xxxxxxxxxxxxxx>]

Hi Ed,

We were detecting the microwave noise with the door SHUT, while boiling a 
large cup of water.

We did NOT defeat anything in the unit.  I just had her open the door to 
turn it OFF, and shut the door and hit the ON button to turn it on.  So, 
opening the door is how I had her turn the thing off.

So yes, the array was detecting noise from leakage!  There was enough to 
hear indeed.  And I was on the floor below, about 15 feet from the oven.

Thanks for the good warnings, though.  Rather safe, than sorry :-)

73,

Mark N8MH, Ph.D. in molecular biology ;-)


At 01:53 AM 11/27/2000, Edward R. Cole wrote:
> >From: "Mark L. Hammond" <hammond@surrealnet.net>
> >Do what I did last night.  Turn on your microwave oven, and point your
> >array+downconverter at it :-)
> >
> >Worked like a charm...I had my 9 year old daughter helping.  She got a kick
> >out of opening and closing the door for me.  She didn't know she was
> >actually doing satellite CW ;-)
> >73,
> >Mark N8MH
>
>You did what!?
>
>Mark, did you defeat the safety interlocks in your microwave oven?  By law
>the oven is suppose to stop generating RF the second the door is opened.
>Radiation from an open microwave oven is extremely dangerous!  The RF power
>varies by model from 500w to 1400w.  Safe exposure is <1 mw/sq-cm. for
>short time duration.  I haven't looked up the FCC exposure standard but
>expect it is at least this.
>
>2.4 GHz was chosen for ovens because it is particularly good for heating
>organic tissue {that means YOU!}.  I turns out that human cranial cavity is
>nearly resonant at these frequencies {cook your brains quickly};  Eyes are
>also particularly sensitive and microwave exposure can cause cataracts.
>
>"If you are going to try this at home" {as the caveat in TV advertising
>goes}, keep the door closed and try to detect the weak RF leakage.  I
>haven't tried this but there may be sufficient RF leakage to provide a
>signal.  After all your 2.4 GHz convertor should be able to detect around
>-100 dBm [1/1*10^10 mw].  With a couple feet safety distance {door closed}
>that may reduce to -60 dBm [one millionth mw].  I'm not sure what UL and
>OSHA say about microwave oven leakage standards, but I would suspect it to
>be better than .01 mw [-20 dBm].
>
>DID I SCARE EVERYONE SUFFICIENTLY?  I HOPE SO -- THIS IS SERIOUS!
>
>73, Ed
>PS:  I performed microwave energy transmission studies for NASA in the
>1970's using microwave oven tubes.  We were able to transmit power over
>10-15 miles with 30% efficiency {i.e. we got 300w for transmitting 1000w}.
>The study was for a concept to beam solar powered microwave beams to earth
>as a source of alternative energy...concept was abandoned due to safety
>concerns.
>
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Mark L. Hammond  [N8MH]

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